Typically, exhaust gas recirculation (EGR) valves are employed in engines for reducing various engine emissions. The EGR valve may be disposed between the engine exhaust manifold and the engine intake manifold. In order to effectively reduce the emissions, a position of the EGR valve has to be precisely controlled. In some cases, the EGR valve may be driven by an EGR actuator in a closed loop control mode. Moreover, the EGR actuator may be controlled in an engine operation range according to a predetermined strategy.
The controller may switch to an open-loop control mode when the EGR valve is approaching to a full close position based on predefined parameters that are set during an engine calibration process. However, these predefined parameters for switching modes may vary during an operation life of the engine due to an aging and/or wear of various components. Additionally, when the EGR valve switches control modes, the emissions from the engine may also be impacted.
For reference, U.S. Pat. No. 8,109,258 (hereinafter the '258 patent) discloses a method for diagnosing slow EGR response in an internal combustion engine equipped with an electronic controller with memory. In one embodiment, the method includes passing an EGR setpoint value and an actual EGR value through first order filters to eliminate high frequency noise; determining an actual EGR gradient as a function of any difference between the EGR set point and the actual EGR value while simultaneously determining an actual EGR gradient; and logging a fault in the electronic controller if the expected EGR gradient is greater than the actual EGR gradient by a predetermined amount.
However, the methods of the '258 patent may not take into account a change in the predefined parameters and the impact of the emissions thereof. The present disclosure is directed to mitigating or eliminating one or more of the drawbacks discussed above.